Energy Changes in Chemical Reactions: Mastery Test

Select the correct answer. Some fuel cells are powered by hydrogen. Scientists are looking into the decomposition of water (H₂O) to make hydrogen fuel with the help of the Sun's energy. What challenge do scientists face with this task?

• Decomposing water requires a high activation energy.

• The Sun isn’t a renewable resource.

• Decomposing water results in toxic byproducts.

• Scientists are uncertain what to do with the excess oxygen.

Select the correct answer. Which chemical reaction shows photosynthesis?

• water + carbon dioxide + sunlight → oxygen + glucose

• carbon + oxygen → carbon dioxide

• hydrogen + oxygen → water

• nitrogen + hydrogen → ammonia

Select the correct answer. Which of these reactions is a combustion reaction?

• burning wood

• decomposition of water

• production of food by plants with the help of the Sun's energy

• rotting of fruits and vegetables

Select all the correct answers. Which sentences describe disadvantages of burning fossil fuels instead of using hydrogen fuel cells?

• Burning fossil fuels contributes to climate change.

• Burning fossil fuels takes place inside expensive fuel cells.

• Fossil fuels aren't widely available, but pure hydrogen is.

• Fossil fuels are nonrenewable.

Select the correct answer. In a given chemical reaction, the energy of the products is less than the energy of the reactants. Which statement is true for this chemical reaction?

• Energy is absorbed in the reaction.

• Energy is released in the reaction.

• There is no transfer of energy in the reaction.

• Energy is lost in the reaction.

Select the correct answer from each drop-down menu. A hydrogen fuel cell is more efficient than a combustion reaction because very little of the released energy is released as ________ energy. When used at home, a fuel cell eliminates the need for ________ because the cell is portable.

• electrical energy

• thermal energy

• mechanical energy

• an electrical grid

Select the correct answer from each drop-down menu. In a chemical reaction, activation energy increases the ________ of the reactants. This outcome causes the particles to collide, which results in the ________ of new products.

• temperature

• pressure

• concentration

• formation